ISPConfig only accesable through iP address

I have a weird issue with my new install of ISPconfig. I used the install scrip and installed it on ubuntu 16.04. When I go to the IP address of the host, I am able to log in. When i use the domain name, iSPconfig complains about wrong credentails.

[INFO] I found the following web server(s):
Nginx (PID 11344)
[INFO] I found the following mail server(s):
Postfix (PID 25938)
[INFO] I found the following pop3 server(s):
Dovecot (PID 26911)
[INFO] I found the following imap server(s):
Dovecot (PID 26911)
[INFO] I found the following ftp server(s):
PureFTP (PID 27117)